Influence of re-entrant hexagonal structure and helical auxetic yarn on the tensile and auxetic behavior of parametric fabrics

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The main content of this article theoretically analyzes the yarn diameter and Poisson's ratio variation of braided auxetic yarns under axial strain. Braided auxetic yarns are composed of three components: wrap yarns, the core yarn, and the stiff yarn. The core yarn has a larger diameter and smaller elastic modulus than the other two kinds of yarns, but its rigidity is lower. There is a lack of theoretical basis for predicting the Poisson's ratio of braided auxetic yarn. Based on the geometric model, the curve of the Poisson's ratio has been determined and the Poisson's ratio trend of braided auxetic yarns is deduced, aiming to predict the Poisson's ratio of braided auxetic yarns under axial strain with accurate yarn parameters. The experimental results show that the minimum Poisson's ratio of theoretical value and actual value appears under the same axial strain, and the variation trend of Poisson's ratio of both values is consistent. The Poisson's ratio curve of braided auxetic yarns is predicted, which lays a theoretical foundation for the development of auxetic materials and also provides more possibilities for subsequent research.

Section: Uniaxial Extension Analysismentioning

confidence: 99%

Study on a theoretical model of braided auxetic yarns made from a high-speed braiding machine

Liu

Xiong

et al. 2023

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“…[3][4][5] Some scholars studied the auxetic performance of textile materials, including helical auxetic yarns, double helical auxetic yarns and braided auxetic yarns (BAYs) and auxetic fabrics. [6][7][8][9][10] The main mechanism of the negative Poisson's ratio effect in auxetic yarns is the exchange between the flexible core yarn and the stiff wrap yarn. The core yarn usually has a smaller elastic modulus and a larger radius, and the other stiff yarn has a larger elastic modulus and a thinner radius.…”

mentioning

confidence: 99%

Design, preparation and characterization of braiding auxetic yarns with a high negative Poisson’s ratio

Du,

He,

Liu

2023

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In recent years, research work on auxetic textile materials has become more and more popular. Helical auxetic yarns realize a negative Poisson’s ratio effect at the yarn level, wherein the braided auxetic yarns are prepared to realize the structural stability of the auxetic yarns. However, the degree of the elongation auxetic effect has not been solved. In this paper, composite braided auxetic yarns and re-braided auxetic yarns were successfully fabricated by a ring spinning machine and a high-speed braiding machine, and the Poisson’s ratio curves of the two yarns were tested by image analysis. Through the measurement of the Poisson’s ratios of these two yarns, the experimental results show that they both have a good negative Poisson’s ratio effect, and the degree of auxetic effect increases correspondingly. The composite braid technology makes the auxetic yarns retain the original auxetic effect while the degree of auxetic effect was increased. The preparation of these two kinds of auxetic yarns provides a certain experimental basis for the development of auxetic textile materials in the future, and also provides more improvement ideas for scholars.

“…Many scholars have further studied the structure and mechanical properties of auxetic yarns. [9][10][11] Du et al 6,7 conducted theoretical and relevant experimental analysis on expanded yarn prepared based on ring spinning, and Jiang and Hu. 12 conducted relevant analysis on expanded yarn produced by a braiding machine.…”

mentioning

confidence: 99%

Fabrication and characterization of braided auxetic yarns based on a high-speed braiding machine

Liu

et al. 2022

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In recent years, three kinds of auxetic yarns have mainly been developed, namely helical auxetic yarns based on the ring spinning system and the hollow spindle system and braided auxetic yarns based on the braiding system. However, these auxetic yarns have some drawbacks, such as an unstable structure or no obvious auxetic effect. In this paper, auxetic yarns were successfully braided by wrap filaments and a core filament based on a braiding system, which overcame the slippage problem in the traditional helical yarn structure. Yarns were spun by different structural parameters of the core filament, the wrap filaments and braiding filament, including the diameter ratio, braiding speed and different numbers of wrap filaments. The results showed that all parameters have an impact on the Poisson’s ratio of auxetic yarns and, in addition, the braided auxetic yarns can cause the yarns to be in the pre-stretching state; once the stretching effect occurs, the Poisson's ratio will directly change from a negative value. Since the new auxetic yarns were produced using a high-speed braiding machine and filaments, this would pave the way for their mass production. This provides a certain research basis for mass production of the stable auxetic yarn structure, and based on the realization of the pre-stretching state, it also provides more possibilities for future research.